A branch of cosplaying/roleplaying. When a fan of an anime, manga, game, or movie dresses up as a character of the opposite gender than themselves.
This is sometimes confussing, especially when the person or character they are dressing as has hermaferdiac traits..
Then again, some crossplayers are so good at what they do that they seem to be the same gender as the character they are cosplaying as.
"My friend likes to crossplay as Ed from Fullmetal Alchemist"
"One year I went to Otakon crossplayed as Sango."
"That one crossplayer for Fuuma was was so good that I didn't know it was a girl till she wen't in the girl's bathroom"